I didn't have to sand the table base because I was painting it with chalk paint, which requires no prep. (makingitinthemountains.com)
So wit that said, I did not sand my table but I only removed dust and dirt. (placeofmytaste.com)
Some suggestions: Set up a play dough table; fill a plastic basin with water and let the kids dump, pour, and stir the water (never leave them alone, though — even a few inches of water can present a drowning hazard); stock a small sandbox or sand table with shovels and pails; or put out paper and crayons or finger paints. (babycenter.com)